<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        html,
        body {
            width: 100%;
            height: 100%;
        }

        .box {
            display: grid;
            grid-template-columns: 200px 1fr;
            grid-template-rows: 100px minmax(auto,auto);
            /* justify-items: center; */
            grid-gap: 10px;
        }

        .box>* {
            background-color: skyblue;
            /* width: 50px; */
            /* width: 100px; */
        }

        header {
            grid-column-start: span 2;
        }

        aside {
            /* width: 100px; */
            height: calc(100vh - 20px - 100px - 50px);
            /* margin: 10px auto; */
        }

        footer {
            position: fixed;
            width: 100vw;
            height: 50px;
            bottom: 0;
            background-color: red;
        }
    </style>
</head>

<body>
    <div class="box">
        <header>header</header>

        <aside>aside</aside>
        <div class="main">
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        </div>
        <footer>footer</footer>
    </div>

</body>

</html>